Patent GB-1347877-A (GB)
Title: Process for preparing a zeolite-promoted cracking catalyst
IPC: B01J29/08
Filed: 1971-05-17
Abstract: 1347877 Hydrocarbon cracking catalysts W R GRACE & CO 17 May 1971 [18 May 1970] 15235/71 Heading B1E [Also in Division C5] Hydrocarbon cracking catalyst comprising rare earth metal-exchanged zeolite is prepared by a process which comprises (a) subjecting alkali metal, for example sodium, aluminosilicate zeolite to ion exchange with rare earth metal ions, (b) calcining the rare earth metalexchanged zeolite, for example at a temperature of from 400 to 1500‹F and optionally in a non-oxidizing atmosphere, (c) subjecting the calcined zeolite to ion exchange with ammonium ions, (d) forming a composite comprising the rare earth metal- and ammoniumexchanged zeolite and an oxide matrix and (e) subjecting the composite to ion exchange with rare earth metal ions until the composite has a rare earth metal content (expressed as oxide) of at least 3 weight per cent, preferably of from 3 to 4 weight per cent. The initial rare earth metal ion, exchange step may be effected in two stages; the steps of calcining and ammonium ion exchange may be repeated at least once. Prior to forming the composite, the rare earth metal- and ammonium-exchanged zeolite has an alkali metal content (expressed as oxide) preferably of less than 1 weight per cent and may be calcined, for example at a temperature of 700‹F. The zeolite preferably is composited with the oxide matrix during formation of the matrix; the composite may be formed by a procedure which comprises conventional drying of a mixture containing the constituents of the composite at a temperature above 350‹F or spray drying a slurry containing the constituents of the composite, for example at a temperature above 800‹F. After the final rare earth metal ion exchange step, the composite has an alkali metal content (expressed as oxide) preferably of less than 0.1 weight per cent, for example less than 0.06 weight per cent. Each rare earth metal ion exchange step may be effected using an aqueous solution of a rare earth metal chloride, sulphate, nitrate, formate or acetate; rare earth metals are defined as scandium, ythium and elements having atomic numbers of from 57 to 71. The zeolite, which may constitute from 2 to 30 weight per cent of the composite, may be natural or synthetic, for example selected from chabasite, erionite, faujasite, mordenite, sodalite and zeolites A, X, L and Y; the oxide matrix may be selected from silica, alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-alumina-magnesia, silica-alumina-zirconia and clays, including semi-synthetic clays. As exemplified, catalysts comprising a silicaalumina matrix are prepared by mixing a slurry containing zeolite (prepared by a procedure wherein sodium-form zeolite X is contacted with rare earth metal chloride solution in two stages, calcined at 1000‹F, contacted with ammonium sulphate solution in two stages and dried) and a slurry containing silicaalumina (prepared by a procedure wherein aqueous sodium silicate solution is gelled with carbon dioxide, aluminium sulphate solution is added to the resulting silica gel, sulphuric acid is added to the resulting mixture to precipitate alumina and the resulting silica-alumina gel is homogenised and spray dried), contacting the resulting slurry with rare earth metal chloride solution, filtering the thus-contacted slurry, drying the resulting filter cake at 220‹F, washing the dried filter cake by slurrying in water, filtering the resulting slurry, washing the resulting filter cake with water while on the filter, and drying the washed filter cake at 220‹F. A comparison catalyst is prepared by a similar procedure wherein the final contact with rare earth metal chloride solution is omitted.